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Print warnings when backwards timestamps are detected.

Browse Source 
Bug: 7100774

Change-Id: I752fd1680b32ce33d17d6042d6c82e27d7ba9dd2
This commit is contained in:
Ben Cheng 2012-09-14 14:45:34 -07:00
parent ae2cfb5746
commit 8dc7c6e659
1 changed files with 55 additions and 5 deletions
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60
libs/utils/SystemClock.cpp
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@ -109,6 +109,43 @@ int64_t elapsedRealtime()
return nanoseconds_to_milliseconds(elapsedRealtimeNano());
}
#define METHOD_CLOCK_GETTIME 0
#define METHOD_IOCTL 1
#define METHOD_SYSTEMTIME 2
static const char *gettime_method_names[] = {
"clock_gettime",
"ioctl",
"systemTime",
};
static inline void checkTimeStamps(int64_t timestamp,
int64_t volatile *prevTimestampPtr,
int volatile *prevMethodPtr,
int curMethod)
{
/*
* Disable the check for SDK since the prebuilt toolchain doesn't contain
* gettid, and int64_t is different on the ARM platform
* (ie long vs long long).
*/
#ifdef ARCH_ARM
int64_t prevTimestamp = *prevTimestampPtr;
int prevMethod = *prevMethodPtr;
if (timestamp < prevTimestamp) {
ALOGW("time going backwards: prev %lld(%s) vs now %lld(%s), tid=%d",
prevTimestamp, gettime_method_names[prevMethod],
timestamp, gettime_method_names[curMethod],
gettid());
}
// NOTE - not atomic and may generate spurious warnings if the 64-bit
// write is interrupted or not observed as a whole.
*prevTimestampPtr = timestamp;
*prevMethodPtr = curMethod;
#endif
}
/*
* native public static long elapsedRealtimeNano();
*/
@ -117,8 +154,15 @@ int64_t elapsedRealtimeNano()
#ifdef HAVE_ANDROID_OS
struct timespec ts;
int result = clock_gettime(CLOCK_BOOTTIME, &ts);
int64_t timestamp;
static volatile int64_t prevTimestamp;
static volatile int prevMethod;
if (result == 0) {
return seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
timestamp = seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
checkTimeStamps(timestamp, &prevTimestamp, &prevMethod,
METHOD_CLOCK_GETTIME);
return timestamp;
}
// CLOCK_BOOTTIME doesn't exist, fallback to /dev/alarm
@ -129,18 +173,24 @@ int64_t elapsedRealtimeNano()
if (android_atomic_cmpxchg(-1, fd, &s_fd)) {
close(fd);
}
result = ioctl(s_fd,
ANDROID_ALARM_GET_TIME(ANDROID_ALARM_ELAPSED_REALTIME), &ts);
}
result = ioctl(s_fd,
ANDROID_ALARM_GET_TIME(ANDROID_ALARM_ELAPSED_REALTIME), &ts);
if (result == 0) {
return seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
timestamp = seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
checkTimeStamps(timestamp, &prevTimestamp, &prevMethod, METHOD_IOCTL);
return timestamp;
}
// XXX: there was an error, probably because the driver didn't
// exist ... this should return
// a real error, like an exception!
return systemTime(SYSTEM_TIME_MONOTONIC);
timestamp = systemTime(SYSTEM_TIME_MONOTONIC);
checkTimeStamps(timestamp, &prevTimestamp, &prevMethod,
METHOD_SYSTEMTIME);
return timestamp;
#else
return systemTime(SYSTEM_TIME_MONOTONIC);
#endif